Modern network applications are widely used, and the quantities of data transferred between the individual network nodes are rising continuously with the progressive development of the various network applications. The video-on-demand (VoD) services as well as large file transfers for distributed simulations, such as grid computation applications, may be mentioned here as examples of network applications which require a wide bandwidth.
TCP (Transmission Control Protocol)-based data transmissions (using standard operating parameters) achieve a transmission rate of about 5 Mbit/s to 8 Mbit/s in a WAN environment. Recently, new protocols have been developed which allow high-speed data transmission at a transmission rate of about 1 Gbit/s, such as rate-based overload control protocols, which include FOBS (Fast Object-Based Data Transfer System) and FRTP (Fixed Rate Transport Protocol). These protocols allow high-bit-rate data transfer in networks with high bandwidth/delay products.
FIG. 1 shows a comparison of the throughput of rate-based overload control mechanisms using RTT (Round Trip Time)-based approaches (such as the TC protocol) for increasing data packet loss, on the basis of a first graph, in which the throughput is plotted on the ordinate, and the data packet loss is plotted on the abscissa, as percentages.
In the first graph, the dashed first lines L1, L1′ relate to a data transfer for which a transport protocol based on rate-based overload control is used, while the solid first curve K1 relates to a data transfer using an RTT-based TCP protocol.
In the case of the graph L1, L1′, the throughput is maintained even when the data packet loss rises. However, when the data packet loss exceeds a specific value, the data rate falls to zero. In contrast to the rate-based approach, the throughput falls continuously in the case of data transfers which use RTT-based overload control, such as the TCP protocol, although a low throughput can be achieved even with a high data packet loss or long RTT delays.
FIG. 2 shows a second graph, in which the throughput is chosen as the ordinate, and the RTT delay as the abscissa. In the second graph, the dashed second lines L2, L2′ relate to a data transfer for which a transport protocol based on rate-based overload control is used, while the solid second curve K2 relates to a data transfer by means of an RTT-based TCP protocol.
The graphs in both FIGS. 1 and 2 are similar.
As is evident from the embodiments described above, the current network protocols for distributed applications are capable of further development with regard to the requirements placed on them. On the one hand, rate-based overload control approaches allow high-speed data transmissions with a high throughput up to a specific threshold value, where the data rate collapses. On the other hand, transport protocols which are based on rate-based overload control do not allow high throughput rates, but offer reliable data transmissions even in the event of a high data packet loss or a long RTT delay.